Thousands of South Koreans protest the US' missile defense system

North Korea is believed to be close to mastering the technology necessary to test an intercontinental ballistic missile, a weapon able to impact South Korea's defense strategy and those of its allies.

Reuters/Kim Kyung-HoonA North Korean flag is pictured at its embassy in Beijing January 6, 2016.

North Korea's test on Thursday could be for the smallest stage of an intercontinental ballistic missile (ICBM) rocket engine, said the U.S. official, who spoke on the condition of anonymity.

North Korea this year has tested several new missile systems, including a powerful mid-range missile experts say could one day reach targets as far as Hawaii or Alaska. The silence from the Pyongyang-based news agency is surprising given the regime's usual practice of reporting on their military tests for propaganda.

China is seen as North Korea's main ally and the U.S. hopes Beijing can have greater influence on the state to stop both its missile tests and nuclear program.

Participation in Pyeongchang could "provide a turning point for the reconciliation between the South and North", Moon said. The different kinds of missiles tested, which the Kim Jong-un regime hopes to soon mate with nuclear warheads, were capable of ranges from about 600 miles to over 3,000 miles. These guided missiles are primarily designed for the delivery of nuclear weapons, and each of these missiles could potentially carry more than one thermonuclear warheads. "We have worked closely and have been fully transparent with the South Korean government throughout this process", United States Forces Korea wrote to the Korea Herald on Friday, when asked to respond to Moon's comments.

But the centre-left Moon is known to favour engagement with the North to bring it to the negotiating table in a break from his conservative predecessors who took a hardline stance.

The military activities of South Korea's communist neighbor, including its nuclear arms development programs, apparently motivated the alleged plot, Asahi Shimbun notes. "The result is the reality you see today - North Korea continuing to advance its nuclear and missile program".